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Topic: Can Windows volume slider control hardware volume in USB DAC? (Read 390 times) previous topic - next topic
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Can Windows volume slider control hardware volume in USB DAC?

I have USB DAC that does mute its output when input is digital silence. In moment of muting and unmuting there is soft but audible pop.
Wnen using foobar2000 ans its WASAPI exclusive output, i can use DSPs (this or this)that add noise to least significant bit and thus avoid digital silence on DAC input ans avoid pops.
When noise is added into 24th bit and i lower output volume in foobar2000 more than 6 dB, obviously 24th bit is shifted down and lost. This is how software volume control works. So there is digital silence again and pops on muting/unmuting.
But if in the same situation i use windows volume control for my DAC instead of fb2k volume control, even if i lower volume more than 6 dB, there are still no pops. So it seems that 24th bit is not lost.
In this case windows volume control does not add noise by itself, i checked: if there is no active noise DSP in fb2k, then lowering volume with windows volume control doesn't change behavior of DAC - there are pops on muting/unmuting when digital silence occurs.
So, in this case behavior of windows volume control is not like software volume control.
Can it be that windows volume slider somehow controls hardware volume in DAC?
But my DAC (Dr. DAC2 DX) uses PCM1798 DAC and according to datasheet PCM1798 doesn't support volume regulation. There is no mentioning anywhere of any volume regulator for Dr. DAC2 DX except common analog potentiometer.

 

Re: Can Windows volume slider control hardware volume in USB DAC?

Reply #1
So it seems that 24th bit is not lost.

Depends.
When using 24 bits program material on a 24 bit DAC we do loose resolution using volume control.
In case of a 48 dB reduction, we have 16 bits of resolution left.

111111111111111111111111
000000001111111111111111

However, this is about the audio, the samples.
The Windows mixer converts to float, mixes, dither, convert back to integer.
I do think it likely bit 24 always being dithered when using the win audio stack hence no digital silence.
TheWellTemperedComputer.com

Re: Can Windows volume slider control hardware volume in USB DAC?

Reply #2
The Windows mixer converts to float, mixes, dither, convert back to integer.
I do think it likely bit 24 always being dithered when using the win audio stack hence no digital silence.
Isn't this only true for shared mode? As i wrote i am using exclusive mode.
And
In this case windows volume control does not add noise by itself, i checked: if there is no active noise DSP in fb2k, then lowering volume with windows volume control doesn't change behavior of DAC - there are pops on muting/unmuting when digital silence occurs.

Re: Can Windows volume slider control hardware volume in USB DAC?

Reply #3
A traditional DAC chip like your PCM1798 does not support USB input, as well as other inputs like PCI, Firewire and so on. So there is another interface chip to convert these protocols to I2S, which the DAC chip understands, for example, XMOS, C-Media, customized FPGA/ASIC/microcontroller... The mute and volume control functions could be implemented in these chips, the more powerful ones even support advanced features like EQ, reverb, chorus etc like the ones from Creative gaming products, or studio interfaces from MOTU, RME and so on.

As for simple stuff like mute and volume control, the product manufacturers probably don't see these things as a selling point and they don't even mention it.

WASAPI exclusive mode and ASIO only bypass the Windows mixer, it does not bypass the driver, the driver can still perform additional processing, or instruct the underlying hardware DSP to do additional stuff.

Re: Can Windows volume slider control hardware volume in USB DAC?

Reply #4
As expected...
X

https://www.macnica.com.tw/en/products/semiconductor/tenor/te7022lnot-recommend-new-project

TE7022L is a low power, cost-effective, USB 2.0 Full-Speed compliant Audio Streaming Controller. It features one independent stereo playback and recording pairs and one IEC60958 S/PDIF receive and transmit streaming pair with independent volume control, supporting 16/24-bit resolution and up to 96K Hz sampling rate.